Flat tube evaporator with vertical flat tubes for motor vehicles

ABSTRACT

The invention relates to a flat tube evaporator for motor vehicle air conditioning equipments with flat tubes ( 2 ), the longitudinal extension direction of which is vertical, and zig zag fins ( 8 ) arranged between the flat tubes ( 2 ), against which the external heat exchange fluid can flow (arrow  9 ). According to the invention it is provided that a water flow gutter ( 50 ) extending downwards on both sides of the flat tubes ( 2 ) is designed next to the rear end region ( 52 ) of the zig zag fins ( 8 ), seen in the flow direction (arrow  9 ) of the external heat exchange fluid.

[0001] The invention relates to a flat tube evaporator, preferably of aluminum or an aluminum alloy, for motor vehicle air conditioning equipments with the features of the preamble of claim 1. Such a flat tube evaporator is for example known from U.S. Pat. No. 4,350,025.

[0002] In the operation of a flat tube evaporator for motor vehicle air conditioning equipments, there is a general tendency to avoid a blowing through of condensation water or other humidity during the flow of external heat exchange fluid, generally air, to regions further in the back of the motor vehicle air conditioning equipment where the occurance or even the accumulation of humidity can be disturbing or even harmful.

[0003] In a known multi-flow flat tube evaporator, in which separately finished flat tubes are assigned to the individual flows, vertical openings remain between these separately finished flat tubes, which can also be used, if needed, as vertical drains for accumulated humidity. Water let off in this manner can be collected in a collecting basin and drained, if necessary (EP-A2-0 709 643).

[0004] There are, however, problems concerning the water drainage, if the flat tube is provided in a non-divided manner. Such a non-divided use of flat tubes, however, is more convenient concerning the manufacture than the assembly of separately finished flat tubes. The flat tube evaporator according to the U.S. Pat. No. 4,350,025 already guarantees a drainage of humidity, which can occur within the ribbing by the zig zag fins, especially when using only one-part flat tube arrangements. Experience shows that occuring humidity, such as in particular condensation water, is first of all entrained by the external heat exchange medium in the ribbing by the zig zag fins and accumulates only at the end of the flowing path through the ribbing. In the flat tube evaporator according to the U.S. Pat. No. 4,350,025, following the rear end region of the zig zag fins, seen in the flow direction of the external heat exchange fluid, a water flow gutter each continuously extending downwards is therefore finished at the projecting part integrally finished with the flat tube at the narrow front side of the flat tube and being formed by a T-profile, the central web of which is connected to the narrow front side of the flat tube and which projects over the zig zag fins in the flow direction of the external heat exchange fluid.

[0005] In this known flat tube evaporator, the T-shaped projections to the end regions of the flat tubes, seen in the flow direction of the external heat exchange fluid, increase the amount of material necessary and the structural depth of the flat tube evaporator and necessitate an expensive manufacture technology. Moreover, the projections freely projecting from the zig zag fins cannot take up and drain humidity which adheres within the region of the zig zag fins as drops and thus cannot reach the water flow gutters arranged behind the zig zag fins with respect to the flow direction thereof from the external heat exchange fluid.

[0006] Therefore, the object underlying the present invention is to achieve an efficient water drain function from the zig zag fins with a simple manufacture technology without necessitating an additional amount of material or a greater structural depth.

[0007] This object is solved in a flat tube evaporator according to claim 1.

[0008] In a flat tube evaporator, the plates of which extend vertically as do the flat tubes and between the plates of which zig zag fins are internested, it is know per se to design a vertical water flow gutter at the outer side of each plate. The ducts of the plates of flat tube evaporators, however, comprise relatively thick walls, in which the design of such a water flow gutter is much less problematic than in flat tubes in which the design of such a gutter directly within the flat tube region, in the interior of which the individual ducts extend, is always connected with an influence on the duct cross-section due to the indentation, by which the condensation water flow gutter is to be formed. Such an arrangement of a vertical condensation water flow gutter in the flat outer side of a flat tube therefore requires considerations not taken into account in the past, concerning the extent to which the complete thermodynamic operation of the flat tube evaporator can be maintained with a good efficiency. In this sense, the concrete solution of claim 2 is original.

[0009] According to the invention, one can additionaly design the flow gutter necessary in each case without any additional efforts as concerns the manufacture, the material and the construction during the cutting into sections of the flat tubes from a coil by impression. In the process, one can, if necessary, provide several water flow gutters by indentations and thus collect and drain—practically in statu nascendi— accumulated condensation water still in the extension region of the zig zag fins, in case of an early accumulation of condensation water in the package of the zig zag fins even already after an optionally relatively short partial path of the cross-flow.

[0010] The further embodiment according to claim 2 is especially interesting when the ribbing by means of the zig zag fins comprises limbs relatively narrowly adjacent to one another. Namely, it has shown that then on the one hand the shaping according to claim 2 in the manufacture of the flat tube evaporator is still relatively easy and that on the other hand the relatively narrow distance between the limbs of the zig zag fins adjacent to the water flow gutter leads to the fact that humidity automatically accumulates at this narrow part, gradually increases and becomes a major accumulation and finally, when it has increased to reach to the condensation water flow gutter, can be drained to this gutter essentially without residues. This further opposes to an entraining of humidity in the flow direction by means of the incoming flow of the external heat exchange fluid.

[0011] For the function of the invention, it is therefore necessary that the flow gutters are provided in the region of the fins, where the condensation water accumulates. Such flow gutters, however, are disturbing at the connection ends of the flat tubes where a soldering or brazing, e.g. with a tube bottom, is effected. In this case, claim 3 provides to do without the indentation in the brazed region which can form the water flow gutter. For this purpose, according to the U.S. Pat. No. 4,350,025, the T-profile web provided therein had to be separately cut off, which requires a complicated finishing, for example by sawing out of the piece or milling off. Within the scope of the invention, the same effect can be easily achieved by not additionally forming from the beginning the indentation in the end regions of the flat tubes when cutting them off the coil.

[0012] The invention will be illustrated more in detail with schematic drawings and several embodiments as follows, wherein:

[0013]FIG. 1 shows a perspective view of a flat tube evaporator, in which the longitudinal extension of the flat tubes 2 is vertical;

[0014]FIG. 2 shows a cross-section in the flow direction of the external heat exchange fluid through a section of the block arrangement of flat tubes and zig zag fins with a detailed representation at the rear end of the representation of FIG. 2, seen in the flow direction of the external heat exchange fluid; and

[0015]FIG. 3 shows in an enlarged scale a plan view on a zig zag fin internested between two adjacent flat tubes with a view into the flow direction of the external heat exchange fluid.

[0016] The flat tube evaporator represented in FIG. 1 has a double-flow design and is embodied as an evaporator of a refrigerant circulation.

[0017] This does not exclude to transfer the gist of the represented features to flat tube heat exchangers having a different number of flows.

[0018] The flat tube evaporator comprises the following general design:

[0019] A major number of typically twenty to thirty flat tubes 2, which extend vertically, is arranged at constant distances to each other and with aligned front sides 4. Between the flat sides 6 of the flat tubes, a zig zag fin 8 each is internested in a sandwiched fashion. Similarly, a zig zag fin 8 each is furthermore arranged at the two outer surfaces 4 of the outer flat tubes. Each flat tube comprises internal reinforcing webs 10, which division off chambers 12 in the flat tube acting as continuous ducts. Depending on the structural depth, a number of the chambers or ducts 12 of ten to thirty is typical.

[0020] The stated typical regions of the number of flat tubes 2 and the chambers 12 thereof is intended to be only a preferred number and is not intended to be restricting.

[0021] In a motor vehicle air conditioning equipment, in the final state outer air as an external heat exchange medium flows in the direction of arrow 9 shown in FIG. 1 and FIG. 3 in the direction of the structural depth through the block arrangement of the flat tubes 2 and the zig zag fins 8.

[0022] In the evaporator, a refrigerant, such as preferably fluorohydrocarbon, serves as internal heat exchange medium which enters the heat exchanger via a supply line 14 and exits the heat exchanger via an outlet line 16. In the refrigerant circulation, the supply line 14 comes from the liquefier thereof. The outlet line 16 leads to the condensor of the refrigerant circulation.

[0023] A distribution of the refrigerant on the inlet side is effected from the supply line 14 to the individual flat tubes by a so-called distributor. On the outlet side, the refrigerant is supplied as a whole to the outlet line 16. Though it is possible to assign the distribution and the collection to separate boxes, both functions are combined in a common header 18.

[0024] This header 18 is then arranged at a front side 4 of the flat tubes 2, while at the other front side 4 of the flat tubes 2, a flow reverse takes place only between each of the flows, here for example in common deflection header 22 according to FIG. 1.

[0025] In the borderline case of a single-flow heat exchanger, the deflection header 22 would be replaced by a not shown outlet header.

[0026] The multi-flow design means at least one flow reverse in the region of the individual ducts formed by the chambers 12 in each flat tube 2. In the shown double-flow design—the two flows of which are separated from one another by a reinforcing web 10 a in each flat tube according to FIG. 1—the deflection header 22 does then not need any further intermediate chamber subdivision, it is only necessary that a single deflection function is guaranteed. In case of a more than double-flow deflection, in the deflection header 22 at least one parting wall is necessary, so that for example in case of a four-flow design, a double simple deflection in the respective deflection header 22 is effected. In a design with an even greater number of flows, the number of parting walls optionally has to be increased.

[0027] Without restricting the generality, the header 18 is composed of a tube bottom 26 and a cap 28, wherein optionally further parts for constructing the header 18 can be provided.

[0028] The free ends of the tubes 2 opposite the deflection header 22 tightly engage the tube bottom 26 in communication with the inner space of the header 18, which tube bottom is correspondingly provided with engaging slits as well as with corresponding internal and/or external engaging muffs.

[0029] As in the header 18, the inlet function and the outlet function of the refrigerant are combined, the header 18 requires at least a two-chamber design which separates an inlet side from the outlet side. For this purpose, the chamber subdivision comprises at least one flat web in form of a longitudinal web 32, which separates the inlet region in the header 18 communicating with the supply line 14 from an outlet chamber 34 continuously extending longitudinally of the header 18 and communicating with the outlet line 16.

[0030] In the evaporator, furthermore the supply of the refrigerant on the side of the inlet to all flat tubes 2 has to be as steady as possible. In a borderline case, the supplied refrigerant can be supplied to each individual flat tube 2 by a so-called distributor. In most cases, however, the supply is effected to adjacent groups of flat tubes 2, in which at least some groups comprise a number of flat tubes higher than one, wherein the number of flat tubes 2 per group can also vary. An own inlet chamber is assigned to each group of flat tubes 2, which chamber directly communicates with the respective group of the flat tubes 2. The own inlet chambers are divisioned off from one another in the chamber subdivision by crosswise webs designed as flat webs.

[0031] In the double-flow evaporator, the crosswise webs depart at a right angle only from one side of each of the longitudinal webs 32.

[0032] In a four-flow evaporator, apart from the longitudinal web 32 contiguous to the outlet chamber 34, another longitudinal web in parallel to this web is provided. This web is intersected at a right angle by the crosswise webs divisioning off the own inlet chambers of the groups of flat tubes up to the connection to the longitudinal web 32. In the elongation of the crosswise webs between the two longitudinal webs, between each of these longitudinal webs an inner deflection chamber contiguous to the respective outer own inlet chamber for deflecting the second flow into the third flow is divisioned off within the header 18.

[0033] In case of greater numbers of flows which are guided through the header 18 with a deflection function, the number of the longitudinal webs as well as the number of the inner deflection chambers increase correspondingly, the deflection chambers then being furthermore internested in the crosswise direction of the header situated internally and one next to the other between the own inlet chambers of the groups of flat tubes 2 as well as the outlet chamber 34.

[0034] The supply line 14 communicates with each of the individual inlet chambers via an own supply line 44 extending in the header 18, the design of which can vary, e.g. coordinated in a tube.

[0035] In the assembled heat exchanger, the block of flat tubes 2 and zig zag fins 8 is laterally terminated by a side sheet metal 36 in contact with each of the outer zig zag fins, such that the side sheet metals 36 form an outer frame for the outer air flowing against the heat exchanger block according to arrow 6 in FIG. 2.

[0036] The flat tubes 2, the zig zag fins 8, the tube bottom 26 and the cap 28 of the header together with the optionally provided chamber subdivision as well as the side sheet metals 36 of the heat exchanger consist, as well as conveniently the supply line 14 and the outlet line 16, of aluminum and/or an aluminum alloy and are brazed including the sections of the line connections adjacent to the heat exchanger to form the finished evaporator.

[0037] Though it is not shown, in practice in refrigerant evaporators for motor vehicle conditioning equipments, according to FIG. 1, optionally the supply line 14 and the outlet line 16, which can pass over into the header 18 via corresponding connecting sleeves, are connected to two respective connecting sleeves of a thermostatically controlled block valve. At the opposite side, which is not visible, this valve comprises two further connecting sleeves at the side of the inlet and of the outlet.

[0038] The tube bottom 26 and the cap 28 are formed of sheet metal pre-coated with solder or braze, respectively. Here, the free edge of the cap engages the tube bottom 26 with an overlap at least on one side.

[0039] Considering first of all FIG. 3, one can see that the corresponding sectional representation runs through a duct 12 of two flat tubes 2 extending in parallel and vertically to one another. The following statements, however, are also applicable when a section would be considered which ran through a reinforcing web 10 each of the same flat tube 2.

[0040] The special arrangement of a zig zag fin 4 at a right angle to the flow direction of the external heat exchange fluid 9 is represented with a view in the flow direction. The individual limbs 38 of the zig zag fin extend here in the flow direction of the arrow 9 of the external heat exchange fluid and are connected via rounded apexes 40 in the continuation direction of the zig zag fin, i.e. in the vertical direction. Each of the apexes 40 are fixed by brazing zones 42 at the adjacent flat side of the adjacent flat tube 2. The arrangement and the embodiment of the limb 38 and the apex 40 are selected such that the free flow cross-section for the external heat exchange fluid according to arrow 9 is greater within the turn of the apexes 40 than in the region of the free distance 44 of two apexes 40 adajacent to the same flat tube 2. Thus, the space 46 between adjacent limbs 38 of the zig zag fin 8 has a narrower design in the region of the free distance 44 than adjacent to the apex 40. This leads to the fact that in the region of the narrow gap defined by each of the free distances 44 under the influence of surface tensions, capillary depositions 48 from humidity entrained by the external heat exchange fluid can occur.

[0041] These depositions 48 of liquid accumulate at the rear ends of the width extension of the zig zag fin 8 or the limbs thereof 38, respectively, seen in the flow direction of the external heat exchange fluid according to arrow 9. Within the scope of the invention, it is taken care that in an arrangement and an embodiment of the zig zag fins according to FIG. 3, or also in a comparable arrangement and embodiment with respect to the creation of liquid depositions 48, it is guaranteed that the depositions 48 do not remain in the zig zag fin 8 and reduce the clear cross-section thereof, but are purposefully drained at least from time to time.

[0042] For this purpose, it is helpful to arrange a device draining the accumulated liquid adjacent to the liquid depositions 48, that is in the rear region seen in the flow direction of the external heat exchange fluid according to arrow 9.

[0043] For this purpose, in all three represented embodiments, adjacent to the rear end of the zig zag fin 8 or of the limbs 38, respectively, thereof, seen in the flow direction of the external heat exchange fluid according to arrow 9, a water flow gutter 50 vertically and continuously extending downwards is designed at each of the two adjacent flat tubes 2.

[0044] Here, in all embodiments it is started from the fact that the zig zag fin 8 projects in the direction of arrow 9 from each of the adjacent flat tubes 2 with an overhang 52, which is a feature generally convenient for the realisation of the invention.

[0045] Corresponding to the embodiment according to FIG. 2, the respective vertical water flow gutter 50 is designed by a vertical indentation 60 at the flat side of the contiguous flat tube 2 facing the adjacent zig zag fin, wherein the indentation can be conveniently effected at the wall surface of a duct 12. Though the indentation 60 in question can also be effected in the last duct 12 of the respective flat tube 2, seen in the flow direction of the external heat exchange fluid according to arrow 9, FIG. 2 shows that likewise the water flow gutter can be designed in a preceding duct, here in the last but one duct seen in the mentioned flow direction. Here, it is convenient that each of these indentations faces a free distance 44 each between adjacent limbs 38 of the zig zag fin.

[0046] As furthermore can be seen from FIG. 1, the connection ends 62 of the flat tubes 2 are kept free from the respective indentation 60. 

1. Flat tube evaporator, preferably of aluminum or an aluminum alloy, for motor vehicle air conditioning equipments with flat tubes (2), the longitudinal extension direction of which is vertical, and zig zag fins (8) arranged between the flat tubes (2), against which the external heat exchange fluid, preferably air, can flow (arrow 9) longitudinally of the apexes (40) of their limbs (38) extending in a zig zag manner, wherein a water flow gutter (50) is designed in continuous extension downwards on both sides of the flat tubes (2) following the rear end region (52) of the zig zag fins (8) seen in the flow direction (arrow 9) of the external heat exchange fluid, characterized in that the water flow gutter (50) is shaped at the outer surface as an indentation (60) of the flat side of the flat tube (2) and is adjacent to the rear end region (52) of the zig zag fins (8) seen in the flow direction (arrow 9) of the external heat exchange fluid.
 2. Flat tube evaporator according to claim 1 , characterized in that the design of the space (46) between adjacent limbs (38) of the zig zag fin (8) is narrower (at 44) adjacent to the water flow gutter (50) than adjacent to the apex (40).
 3. Flat tube evaporator according to claim 1 or claim 2 , characterized in that the connection ends of the flat tubes (2) are kept free from the respective indentation (60). 